Abstraet--A new approach is described to computer simulate cation distribution in octahedral sheets of dioctahedral 2:1 layer silicates with vacant trans-octahedra. This approach makes use of the information on cation distribution at the one-dimensional level provided by integrated IR optical densities for the region of OH-stretching frequencies. By using this program it is possible to show that (1) the Mrssbauer spectrum of glauconite B. Patom conforms to the structural model composed of celandonite-like and illite-like domains whose dimensions are limited by approximately 2 or 4 unit cells; (2) non-equivalency of "left" and "right" cis-positions (with fixed b-direction) with respect to R 2 § and R J § occupancy is a characteristic feature of a celadonite-like domain.